I think your point about AT weapons already being modeled around caliber specific damage actually helps my case. The interaction of damage, accuracy, rate of fire and range is already there, using caliber specific damage and it works!
You can see the squads heal bar dropping with each shot and by which you can estimate how many more hits it will take to drop a model when you factor in how many models are left in the squad. In this case tanks and infantry work much the same way where you look at the unit icon, compare it to what’s shooting at you and thus determine how many hits the squad or vehicle can take. Simply, I would say that yes, you can see how much health a model has left and make decisions based on that.
And, once again, this is about CoH 3. In CoH 3 you might actually be able to see how much HP an individual model has left in it. Is that something you’d like to see?
In CoH 3 you might have a large health bar for the squad and smaller ones for each model. Or you might have different unit skins that show wounds or limping or bandages that indicate that a model is in good, fair or poor health. That could then translate to an oh crap moment when you look and see that your squad has two members at low heath and know that it will take only two Rifle shots each to kill them in the next fight, rather than look and just see a single heath bar at about 3/4 full.
I’m just saying that this system has advantages that exist outside of what CoH 2 has. Think outside the box. Don’t immediately think why a new idea must be bad or why it can’t work, but try to think of why new ideas can work. Innovate.
The whole point to compare it with vehicles is to show how the interaction between infantry and tanks differ.
Vehicles are single entities and besides snipers, infantry units are squad based entities. You exactly know how many shots a tank of your can survive if they all penetrate.
The slower rate of fire and single entity wise damage makes it so you can take timed decisions.
For infantry squads, you could care less if a model deals 8dmg per second or 16dmg per 2s. The amount of "rolls" you make with them is high, that it makes RNG less "swingy". Infantry combat is way more deterministic than tank battles.
Your whole issue is that the game doesn't explain the performance of units. This is why i said information on performance should be provided to the player, mostly using the useless space which describes the units.
Separating the small arm fire weapons into hard coded categories doesn't improve the understanding of the performance of a unit, which on top limits how you can balance unit and breaks other features you are currently unaware off.
Take for example: MGs and suppression.
and i skipped some titles cause i think i made a point with the list i provided. 
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